1. Field of the Invention
The present invention relates to a surface defect inspection apparatus and a surface defect inspection method for inspecting an object for a surface defect.
2. Description of the Related Art
An object of inspection such as a semiconductor wafer is inspected for a surface defect in such a manner that the object being rotated or shaken is visually inspected by an inspector while the front surface of the object is illuminated with illumination light at various angles. In recent years, to decrease fluctuation in inspection quality and improve labor saving and effectiveness of the inspection, techniques to automate this inspection have been studied (for example, refer to Japanese Unexamined Patent Application Publication No. 2003-28621). For inspecting for a surface defect, an apparatus disclosed therein illuminates an object to be inspected with illumination light and receives scattered light emitted from the front surface of the object to be inspected in a predetermined direction. In addition, it is proposed that angle conditions for an illumination system and a light reception system be adjusted to prevent reception of noise light (including specular light and diffracted light) other than scattered light.
However, there are various forms of surface defects on the objects to be inspected. When an object has a defect on the surface such as a concave-shaped flaw which is substantially in parallel with a plane of incidence including the illumination direction of the illumination light and the normal line of the front surface of the object, the above-mentioned apparatus cannot perform an inspection for the flaw properly since the intensity of scattered light emitted from the flaw is very weak. Moreover, if the concave-shaped flaw is curved and a part thereof is substantially in parallel with the plane of incidence, the apparatus cannot inspect for the entire flaw.
Furthermore, even in the angle conditions adjusted as described above, diffracted light may be insufficiently removed, or even if diffracted light is sufficiently removed, the intensity of scattered light may be weak. Thus, it may be not possible to secure an SN ratio necessary for the surface defect inspection.